As used herein, the term ‘power distribution system’ means apparatus for distributing electricity from one location to another in real time. An example of a power distribution system is the UK national electricity distribution system known as the National Grid. Another example of a power distribution system is a vehicle integrated power system (IPS). Such systems are used in the transport industry for transporting electricity throughout a vehicle from a generator to the various systems of the vehicle.
In general, power distribution systems are arranged to carry electrical currents on transmission lines at a specified system frequency. In the UK and Europe, electricity is transported at a system frequency of approximately 50 Hz, whilst in North America electricity is transported at a system frequency of approximately 60 Hz.
In the event that part of a power distribution system experiences a fault, such as a break or a short-circuit in a transmission line, it is desirable to locate that fault as quickly and as accurately as possible so that the fault may be repaired. One way of locating a fault in a transmission line is to look for an apparent change in the impedance of the line at the system frequency. This method is robust, and is typically accurate to within a few kilometers.